This invention relates to sound attenuators or sound reducing devices and in particular to attenuators designed for use on cooling tower, condensing units, evaporative coolers, and similar heat exchanging apparatus.
The use of and construction of cooling towers which can be used to cool large quantities of a liquid such as water is well known in industry. A common type of cooling tower removes heat from water by means of evaporation of some of the water into air that is circulated to the tower. Such cooling towers are often used where water is in limited supply, where there is a need to avoid an undue temperature increase of natural water bodies in the area, where there is a need for water conservation, or where there is a need to avoid pollution.
The more usual types of cooling towers include the forced draft type, the induced-draft type and the hyperbolic tower type. In the first type, one or more fans can be mounted at ground level on or in the tower and these fans can be axial fans or centrifugal fans. Because of the location of these fans, they can be conveniently inspected and maintained. The fans cause air to flow through packing located in the tower structure and water can be piped into the tower to flow down and over this packing to the bottom of the tower where it is collected and then removed. The air flow exits through the top of the tower.
In the induced-draft tower, which is more prevalent in the U.S., an axial fan rotating about a vertical axis can be mounted at the top of the tower structure where the air also exits from the tower. Because of the location of the fan, there is in improved air distribution within the cell of the tower. Again water flows into the tower at an upper level and then flows down through packing located in the tower to a lower level where it is collected and removed. In a counterflow type of tower, the air is introduced into the tower from below while in a crossflow type, air is introduced through openings in the sides of the tower.
The hyperbolic cooling tower utilizes a chimney effect for natural air circulation and thus it does not require the fans of the aforementioned types of cooling towers. This type of cooling tower is not of interest for purposes of the present invention which is directed to reducing the noise level exiting from a cooling tower because of the fan or fans operating therein.
It will be appreciated by those skilled in the art that the construction of both forced-draft and induced-draft towers is well known in the art of cooling liquids such as water for industrial purposes. However one known difficulty with the use of such cooling towers that employ large fans is that they can generate excessive noise, particularly if the cooling towers are to be located in a populated area or in areas where workman or others may frequently be located. Although attempts have been made in the past to reduce the noise level from these cooling towers by the use of sound attenuating apparatus or other means, there remains the need to provide more efficient and better sound attenuating apparatus for use with such cooling towers, particularly apparatus designed for use on top of the cooling tower where the air outlet is normally located.
One known type of sound attenuator that has been used in the past is the type sold by Evapco for its cooling towers that employ centrifugal fans in the bottom thereof. These known sound attenuators include an exterior housing with elongate, straight splitters arranged in the housing between which either the inlet air flow or the outlet air flow must pass. In the case of the fan inlet attenuator, the splitters extend vertically from the bottom to the top of the inlet silencer. In the case of a discharge silencer, these splitters can extend from one vertical sidewall of the housing to an opposite vertical sidewall and they are evenly spaced apart and parallel. The splitters in these silencers can be insulated by the use of sound attenuating material arranged in each splitter. One difficulty with these known discharge silencers is that they are rectangular in plan view while often the outlet opening at the top of a cooling tower is circular, particularly if an axial fan is arranged in the top section of the tower which is often the case with an induced-draft tower.
U.S. Pat. No. 4,232,729 which issued Nov. 11, 1980 to J. P. Ingram et al. describes an air cooled heat exchanger for cooling an industrial liquid, this heat exchanger employing an axial fan that rotates about a vertical axis. Arranged in the top section of the apparatus are a plurality of externally ribbed, hollow cooling sections which are arranged in a plurality of parallel rows. The air flow enters the fan from the bottom of the apparatus and is blown by the fan through these cooling sections to exit from the top of the apparatus. No outlet silencer is provided at the top of this known heat exchanger apparatus.
The use of evaporative coolers and condensing units is also well known in the heat exchanger art. In such coolers, a cooling media is circulated through a cooling coil (horizontal) located below a rotating fan.
It is an object of the present invention to provide an improved sound attenuating apparatus that can be mounted on a cooling tower, condensing unit, or evaporative cooler, this apparatus being very effective at reducing noise levels that can be created by a fan or fans in the tower or unit while at the same time not significantly affecting the efficiency of the cooling tower, condensing unit, or evaporative cooler.
It is a further object of the present invention to provide an improved sound attenuating apparatus suitable for a cooling tower, condensing unit, or evaporative cooler, which can be manufactured and supplied at a reasonable cost.